An engineer must configure traffic for a VLAN that is untagged by the switch as it crosses a trunk link. Which command should be used?
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A. B. C. D.D
The correct answer is D. switchport trunk native vlan 10.
Explanation:
When a VLAN is untagged, it means that the frames that belong to that VLAN are not encapsulated with the VLAN ID when they are sent across the trunk link. Therefore, the receiving switch on the other end of the trunk link will not know which VLAN the frames belong to.
To solve this problem, the switch needs to assign a native VLAN to the trunk link. The native VLAN is the VLAN that is not tagged when it crosses the trunk link. By default, VLAN 1 is the native VLAN for all trunk links.
To configure a native VLAN for a trunk link, the following command can be used:
switchport trunk native vlan <vlan-id>
In this case, the engineer needs to configure traffic for a VLAN that is untagged as it crosses the trunk link. Therefore, the correct answer is D. switchport trunk native vlan 10, where VLAN 10 is the VLAN that needs to be untagged across the trunk link.
The other answer options are incorrect:
A. switchport trunk encapsulation dot1q is used to configure the trunk link to use IEEE 802.1Q encapsulation, which is the default trunking protocol on Cisco switches. This command does not solve the problem of untagged VLAN traffic.
B. switchport trunk allowed vlan 10 is used to specify which VLANs are allowed to cross the trunk link. This command does not solve the problem of untagged VLAN traffic.
C. switchport mode trunk is used to configure the interface as a trunk port. This command does not solve the problem of untagged VLAN traffic.